CStateException -- Exception for invalid state transitions.


#include <CStateException.h>
class          CStateException {
  CStateException(const char* state, const char* allowedStates, const char* pAction);
  virtual const const char* ReasonText();
                  virtual const Int_t ReasonCode();


Many programming problems can be solved by programming a state machine. A state machine, or finite state automaton, simply put, is an entity that has a well defined set of states it can live in. Input stimulii may trigger well defined transitions from one state to another state. For example the begin stimulus can force a run-state machine in the halted state to make a transition to the active state.

When programming a state machine the programmer must take into account exceptional cases where stimulii that are not allowed for the current state are received or, in some cases, errors in implementing the state machine cause the state machine to enter a state that is not legal.

The CStateException provides a class that can be instantiated and then thrown in the event one of these cases occurs.

Public member functions

CStateException(const char* state, const char* allowedStates, const char* pAction);

Creates a CStateException that can be thrown.


The state attempted. This can be a state attemped via an illegal transition or it could be an illegal state actually entered as a result of an error in programming.


The allowed states at this time.


The context in which the error was detected and thrown.

virtual const const char* ReasonText();

As usual, this returns the textual reason for the failure. This will be a string of the form: Invalid object state when: %c relevant erroneous state: %s relevant allowed state: %a Where %c is the context text supplied at construction time. %s is the state that caused the error. %a are the allowed states prior to this error.

virtual const Int_t ReasonCode();

The error code for this exception type is always -1.